1. Field of the Invention
This invention relates to a battery management system for maintaining a charge on auxiliary batteries. The invention specifically relates to a system for automatically coupling auxiliary batteries to the charging system of a vehicle or boat, enabling the auxiliary batteries to be charged from the vehicle or boat charging system when power is available due to operation of the vehicle or boat.
2. Prior Art
Electrical motors are known to run quietly and smoothly. For this reason, relatively small electric trolling motors are popular among anglers for positioning boats while fishing. Electric trolling motors typically are powered from auxiliary storage batteries. Serious fisherman are at disadvantage, however, due to the limited energy storage capabilities of typical storage batteries. For instance, modern electrical storage batteries used with electric trolling motors may provide only approximately three to four hours of usable power. Although it may be possible to use more batteries or larger ones, this can be impractical for reasons of space, weight and expense.
The short battery life of typical storage batteries often adversely affects the fishing enjoyment of serious fishermen. It may take hours to find a spot where the fish are biting or the fish may begin biting at a particular spot at a certain time of day. If the trolling motor batteries discharge completely shortly after the fisherman finds a fishing "hot-spot", one can appreciate the substantial frustration involved.
Serious fisherman may choose to carry spare batteries aboard for a day of fishing. While this may solve the problem of a shortened fishing day, the fisherman is substantially burdened by the need to charge, transport and stow the spare batteries on the boat. Typical lead-acid batteries used to provide electric power to trolling motors are very heavy. Furthermore, they are relatively large thereby taking up valuable space on a fishing boat. A leaking lead-acid battery poses additional problems in the form of potential acid burns to users and damage to the structure of the boat.
Whether or not a number of batteries are provided, the auxiliary batteries must be recharged after use. The batteries are normally removed from the boat, carried to the vicinity of a battery charger coupled to the AC mains, and attached to the charger for an extended period of time. The charger requires attention at least periodically, for example, to avoid overcharging. In the case of a plurality of auxiliary batteries, the user must be present to disconnect the charger when the charge is complete and to connect it to an additional battery or set of batteries.
Prior art battery management and charging systems have been devised, but known systems are unable to eliminate each of the above-listed problems with battery usage. For example, U.S. Pat. No. 3,656,044--King discloses a self-contained battery charging apparatus for charging dead batteries. The apparatus comprises an internal combustion engine coupled to an alternator. The charger is transported to the dead battery and connected to the dead battery for applying charging current. Switching means are provided for connecting battery to the alternator to initiate charging of a completely dead battery.
U.S. Pat. No. 4,081,738--Roller discloses a battery control apparatus for controlling trolling motor batteries. Roller discloses manually operated switches for coupling one or more batteries into a circuit and switching a pair of batteries into a parallel or series configuration across a load. The batteries are switchable for application of a remote charging device or for higher voltage (series) or lower voltage (parallel) use.
U.S. Pat. No. 4,090,122--Hoinski discloses a device for selectively charging one of two batteries provided in an automobile. One battery is the main automobile battery, which powers the ignition and the like; the other is an auxiliary battery for use in providing electric power to auxiliary devices. Switching priority is established such that when the automobile main battery is less than fully charged, the charging system applies charging current to the automobile main battery. After sensing that the automobile main battery is fully charged, the system applies charging current to the auxiliary battery. When both batteries are fully charged, the device disables the charging system as to both batteries. Charging initiation is a function of battery voltage.
U.S. Pat. No. 4,282,475--Milton discloses a DC current supply which converts AC power from domestic mains to a direct current for charging automotive batteries. The disclosure includes a tension releasable power source connector for automatically disconnecting the charger from the source of house current when the vehicle is driven off.
U.S. Pat. No. 4,297,629 Godard, et al. discloses an automatic switching arrangement for switching a pair of batteries between parallel and series configurations. The batteries are switched into a parallel configuration while being charged. The batteries are switched into a series configuration for discharge. Charging means are not disclosed.
U.S. Pat. No. 4,348,628--Loucks discloses a system for charging one of a pair of batteries while the companion battery is powering a vehicle electric motor. When the battery in use substantially weakens, the charged battery is switched into the circuit and the weakened battery is recharged, thus cycling between the two batteries.
U.S. Pat. No. 4,564,797--Binkley discloses a three battery system for use on a vehicle. The system includes one main battery and two alternate batteries. Typically, the main battery is used to provide starting energy and the alternate batteries are connected in parallel for charging. When the main battery is discharged to a point that it lacks adequate charge to provide starting energy, the alternate batteries are switched into a series arrangement for charging the main battery.
Although these and other known devices provide switching means for switching batteries into various configurations, and for applying charging current to batteries, the art does not disclose or suggest a system for automatically switching a pair of auxiliary batteries into parallel configuration with both a main battery and a main battery charging system upon sensed activation of the charging system, and for automatically decoupling the auxiliary batteries from the charging system and coupling them in a series configuration to power a load when the charging system is not activated. The present invention entails a charging system which is particularly apt for maintaining the charge of auxiliary batteries such as trolling motor batteries in this manner, providing a completely automated charging system for constantly maintaining a charge on the auxiliary batteries from a main battery charging system arranged to charge the batteries to a standard charging voltage (e.g., 12V), and for automatically switching the batteries into an optimum configuration for powering a load. The invention thus automatically enables charging or topping off the charge of auxiliary batteries such as trolling motor batteries while operating the primary boat engine on the trip to the fishing site, and loading of the auxiliary batteries for positioning the boat at the site, all at optimum voltages and Without the need for operator intervention.